This invention relates generally to rotary disc calculators and more particularly to an improved rotary disc calculator that may be utilized in many areas including but not limited to the medical field and in particular to an x-ray calculator for use in the medical field.
Rotary disc calculators have been manufactured for many years and generally comprise a plurality of circular discs which are positioned on a central hub and utilize one or more cursor arms which are used by the user of the device in various manipulations and calculations for which the calculator was designed. It is also known to provide various types of spacers or washers between the superimposed disc elements of the calculator primarily for the purpose of separating the adjacent discs a given amount so that each disc is able to be rotated by the user of the device.
Examples of such prior art circular sliderule rotary disc calculators are shown in the following patents issued by the U.S. Patent Office:
______________________________________ Pat. No. Inventor Issue Date ______________________________________ 3,648,025 R. P. Adams March 7, 1972 3,358,920 M. P. Ringley December 19, 1967 3,471,084 J. B. Titus October 7, 1969 3,220,644 N. Gaudio November 30, 1965 ______________________________________
It can be seen from the above cited patents that whenever it is desired by the user of the calculator to rotate one disc without causing adjacent discs to move, the user must hold the disc to to remain stationary while moving the adjacent disc as is the usual practice in calculator manipulation. The reason for this is that there is nothing to prevent one disc from moving the adjacent disc as a result of frictional engagement between the discs. The problem is especially magnified whenever the central hub is tightened with its tightening screw to a degree which will increase the frictional contact between the various adjacent discs.
Such a hand manipulation and holding of the adjacent discs in order to prevent rotation can become especially burdensome whenever the calculator comprises more than two or three rotary discs and is especially burdensome whenever the calculator may comprise for example five or more rotary discs as is common in highly technical calculators such as those used in the medical field and other fields.